This invention relates to electrical terminals that are used for detachably connecting electrical leads to electrical devices.
The invention will be described herein in connection with its use as a pacemaker terminal for connecting and releasing by hand pressure the proximal end of an electrode lead to an implantable heart pacemaker. However, it will be apparent to those skilled in the art that the invention has broader applicability to electrical terminals generally, irrespective of the device to which the lead is to be connected.
The operation of an implantable heart pacemaker requires the transmission of low level electrical signals generated by the heart to the pacemaker, as well as the pacing voltages generated by the pacemaker to the heart. This physical link of transmission, the pacemaker lead, is a section of high-fatigue-resistant, multi-insulated electrical conductor designed to endure the severe environment inside the human body. Any leakage of body fluids or passage of body ions into the conductor can result in a deterioration of the signals transmitted. The distal end of the lead, in the form of an electrode, provides the fixation to the heart tissue. The proximal end of the lead, in the form of a pin, is connected to the terminal of the pacemaker. The materials used to construct the pacemaker lead must be bio-compatible. For insulation, common selections are silicone rubber, epoxy, or polyurethane. For the conductors, common selections are titanium and its alloys, 316L stainless steel and its derivatives, or platinum and its alloys.
Conventional pacemaker terminals utilize a set screw, or "grub" screw, to secure the proximal pin of the lead. A molded silicone rubber top is used to fully encapsulate the terminal, leaving only a sealable opening for the proximal pin to be inserted through. A small, self-sealing slit is cut in the silicone rubber top above the terminal to allow a custom-designed Allen wrench to gain access to the set screw. The set screw design provides good mechanical locking of the proximal pin, along with electrical continuity between the lead and the terminal.
During an implant operation, the surgeon is required to coat the Allen wrench with a special lubricant, locate the external opening of the self-sealing slit in the silicone rubber top, insert the Allen wrench through the slit, engage the set screw, and tighten the set screw to the appropriate torque. If the surgeon fails to perform any of these procedures successfully, there is a chance that the silicone rubber top or the self-sealing slit might become damaged and fail to provide adequate sealing, thereby allowing body fluids to penetrate through to the terminal. This results in deterioration of the heart signals along with corrosion of the terminal and the proximal pin.
Current, new generation pacemakers require the terminals to be more compact in size and more robust in their use. The existing set screw design, limited by the use of an Allen wrench and a threaded hole configuration, has been found to be inadequate not only with regard to compactness, but also with respect to ease of operation.
A primary object of the invention, therefore, is an improved terminal for providing effortless, positive and secure mechanical and electrical connection of an electrical lead to an electrical device, for example an implantable heart pacemaker.
A further object of the invention is an improved terminal for providing effortless, simple and reliable disconnection of the electrical lead from the electrical device, when required.
Another object of the invention is an improved pacemaker terminal which eliminates the need for the use of any special tools, including a set screw, for connecting and disconnecting the proximal end of an electrode lead to a pacemaker terminal.
A still further object of the invention is to prevent body fluids from penetrating into a pacemaker terminal through Allen wrench slits in the silicone rubber top of a pacemaker case.
Yet another object of the invention is to provide a reduction in the size of the pacemaker terminal, and in the overall dimensions of the silicone rubber top therefore.